Grain is cleaned and delivered to a grain storage section of a grain dryer by a hoister, grain feeding is controlled automatically by a material level detector, the operation direction of the grain in the dryer and flow direction of hot wind (cold wind) form a mixed flow, so a whole process of preheating, drying, tempering, drying and cooling is achieved, an angular box has a variable cross-section structure, grain discharge adopts stepless speed regulation at will.Output and precipitation rate are controlled to achieve ideal drying effect, at last, the grain is sent out by a grain discharge machine.